This invention relates to rotary separation units and more particularly to those units used to separate liquids from liquid-bearing materials, such as sludge or sewage.
Horizontal rotary screen units in the prior art were originally and still are used for gravel separations. The openings in the screens of said units are used to grade different sizes of sand and gravel. Later, using the same concept, smaller screens were used to dewater liquid bearing products in so far as letting free-run liquid pass through the screens. It was also found that tilting the rotary unit up on the feed end caused the solid material to flow down and out the discharge end. However, tilting the rotary unit in this manner performed this function only as well as the free-run water would drain through the screens. In many cases the water would not run through the screens properly and the treated material contained as much liquid as when it was fed to the rotary unit.
Even with such rotary units as described above, very fine materials would still be forced through fine screens due to the force with which the materials were fed from the pipe to the unit. In an effort to overcome this problem, some horizontal units in the prior art contained a box which became known as the "head box". The head box was installed inside the machine and its purpose was to slow down the liquid-bearing materials before they hit the screens of the rotary unit so that finer materials remained in the machine instead of piercing through the holes of the screen. Still, however, fibrous materials did not always move toward the discharge end so a series of pitched bars were installed. However, the pitched bars were not sufficient to move the material once the bars became covered with material.
A further problem with the rotary units in the prior art is that the screens inside the cylinder could not be removed easily after becoming clogged with particulates.
An even further problem with rotary units in the prior art is that there was very little control over the time the material spent in the unit, which time determines the dryness of the material discharged from the units.
The instant invention solves the problems associated with the prior art by providing a vastly improved rotary horizontal cylindrical unit which combines improved and novel features to yield an apparatus which can be utilized to separate liquids and solids with efficiency. Moreover, contrary to the rotary units of the prior art, the instant invention has a head box or tray which allows a wider but lower velocity stream to be released over a greater amount of screen area on the interior of the unit. The lower velocity stream eliminates shearing of the flocculated materials which are fed into the invention. Variable and changeable bar screens are also provided so that the size of screen openings can be varied and screens may be removed if and when they become clogged with materials.
Another novel feature, an adjustable dam, is provided at the discharge end of the apparatus. By varying the height of the dam, the "in time" and the dryness of the material being discharged can be controlled. In other words, if less liquid is desired in the end product then the higher the dam is placed. In addition, interrupted pitched and slanted flights or blades, increasing in height from feed to discharge end are provided throughout the interior of the cylinder to better push the sewage toward the discharge end of the device.
Additional features include an inside water backwash system and an outside airspray system which keep particulates from clogging the screen openings. A further optional feature is a heating chamber in the interior of the cylinder which further dries the material therein.